1. Field of the Invention
This invention relates to a multisystem adaptable type signal processing and recording/reproducing apparatus capable of recording various types of input signals and obtaining output signals in various systems in a field of, for example, video tape recorders (which are hereinafter referred to as VTRs) in which various types of recording/reproducing systems are standardized.
2. Description of the Related Art
VTRs for magnetically recording image signals on a magnetic tape including home VTRs may be divided into analog recording systems widely used and digital recording systems developed for broadcasting. In the digital recording system, an amount of information is large and information is generally subjected to the signal compression before the recording operation so as to be used for the home VTR.
As one example of the conventional VTR, analog recording type and digital recording type signal processing systems are described below.
First, the analog recording type signal processing system is explained. VTRs using the analog recording system are roughly divided into several systems including the VHS system and 8 mm system as home VTRs which are now widely used.
A recording signal is picked up from a magnetic tape by use of a reproducing head and amplified by a pre-amplifier. The low-frequency color signal component of an output signal of the pre-amplifier is removed by a high-pass filter (HPF) and separated as an FM luminance signal. The thus separated FM luminance signal is demodulated by an FM demodulation circuit after the level fluctuation in the amplitude thereof is suppressed by a limiter circuit. The frequency of the demodulated luminance signal is restored to the original frequency by a de-emphasis circuit and then the luminance signal is input to a noise compensation circuit for improving the S/N ratio via a drop-out correction circuit. After this, the luminance signal whose S/N ratio is improved is input to a luminance-color (YC) mixing circuit and mixed with a color signal described below.
An output signal of the pre-amplifier is input to a low-pass filter (LPF) and separated as a color signal component. The level fluctuation of the color signal is suppressed by an ACC circuit and then the frequency thereof is restored to a frequency band near the frequency 3.58 MHz of the original color signal by means of a frequency converting circuit and band-pass filter (BPF). After this, the color signal is subjected to a process using a 1H-delay circuit to eliminate the crosstalk, then input to the YC mixing circuit, combined with the luminance signal, and output as a video signal.
The digital recording system includes two types of standards called D-1 and D-2 for broadcasting. When an image signal is recorded in a digital manner, an amount of information is large if the signal is recorded without converting the above standard, and therefore, it becomes necessary to use a tape of large capacity and a large-scale hardware for processing the tape. Thus, an amount of information of image data must be reduced. The method therefor is disclosed in, for example, Japanese Patent Disclosure Nos. H.4-61523, H.4-79696, H.4-79681, H.4-91587, H.4-79688, Japanese Patent Disclosure No. S.54-32240, and Japanese Patent Disclosure No. S.61-196469.
Next, an example of a digital VTR system having an image compression processing function is explained.
An analog input signal is converted into a digital signal by an analog/digital (A/D) converter and divided for each block (which is constructed by 8 pixels in the horizontal direction and 8 lines in the vertical direction) which is a unit used for two-dimensional orthogonal transform by a formatter. Then, a data stirring process called a data shuffling process for each block unit or for each unit of preset number of blocks is effected by use of a buffer memory (Japanese Patent Disclosure Nos. H.4-61523, H.4-79696). After this, the memory output is converted from the time base to the frequency base by means of an orthogonal transforming means (Japanese Patent Disclosure No. H.4-79688), subjected to the quantization process in which it is divided by use of a desired threshold value for each block unit by a quantizing means, and then converted into a variable length code such as a Huffman code by a variable-length coding means (Japanese Patent Disclosure No. H.4-91587). For example, several macro-blocks of the variable-length coded data are stored into three sinks by a data re-arranging means. Important data is collectively stored in one of the three sinks (Japanese Patent Disclosure No. H.4-79681). Additional information (called a parity) which is necessary for error correction in the reproducing operation is added to data subjected to the data re-arrangement by an error correction coding means (Japanese Patent Disclosure No. S.54-32240), and then the data is subjected to the digital modulation such as 8-14 modulation by a modulation means (Japanese Patent Disclosure No. S.61-196469) and output to a recording system.
In the reproducing mode, a reproduction signal from the reproducing system is demodulated by the demodulation means, subjected to the error correction by an error correction decoding means so as to be converted into correct data, and then decoded by a variable length decoding means. The decoded data is inversely quantized by an inverse quantization means and is further converted from the frequency base to the time base by an inverse orthogonal transform means. Then, the data is subjected to the process which is an inverse process of the shuffling in a memory, subjected to the process which is an inverse process of the formatting effected at the time of recording by the formatter, converted into an analog signal by a D/A converter and output.
As described above, the analog recording type and digital recording type VTRs are provided, but a VTR which is a combination of the analog recording type and digital recording type VTRs such as a digital recording/reproducing apparatus which can reproduce an analog reproducing tape recorded in a different system (format) is not provided, for example. Therefore, there may occur a problem that when a digital recording type VTR is made for home use, an analog recording tape cannot be reproduced by use of the digital recording type VTR. Further, various standards are provided for video signals and television receivers of different standards are provided.